The amount of information available on the Internet has grown exponentially. This content can be effectively consumed only through the use of search engines. A growing proportion of content is speech or audio that cannot readily be searched. Speech recognition converts spoken words to text, which allows speech or audio to be searched using search engines.
Speech recognition software development began in the 1980s. Early speech recognition software could recognize words spoken one at a time from a limited vocabulary. The vocabularies could be easily increased but high vocabulary systems were plagued with accuracies under 50% into the early 1990s, rendering most systems practically unusable. The first commercial product to recognize normally spoken continuous speech was released in 1997. The largest improvements in speech recognition software did not come through new developments in speech recognition technique. Instead, the improvements were a result of the increases in computing power and data storage coupled with lowered costs. However, the accuracy rate of commercial products has reached a plateau around 70-80%. Further, attempts to list all possible words in all languages have resulted in one trillion word vocabularies. However, additional, significant increases in recognition accuracy may not be provided by larger vocabularies or increases in computing power or data storage.